Star Wars, The Empire Strikes Back, and Return of the Jedi can be seen as an allegory of the American Revolution...well, if one has a loose definition of "allegory" that is.  Regardless, nothing supports this notion more than a Rebellion taking place against a tyrannical Empire (a conflict still rooted in US Culture) and, of course, The Rebels speaking in American accents and the Imperials British.  

I've always found it extremely strange, and almost disconcerting, that few fans of Star Wars, or even casual watchers of the film, speak of this obvious disparity in accents! It was such a vital element to separating "Us v. Them"/The Rebels from the Empire/the "Good Guys" from the "Bad Guys", yet it's so scarcely acknowledged, and George Lucas of all people seemed to drop it entirely from the Prequels, other than Ewan's Young Obi-Wan and "Darth Sidious" (will never get over that terribly stupid and pointless title).  

Some people on this very Forum, though, have pointed out that Darth Vader, despite being voiced by the Deep South born American James Earl Jones, speaks with British pronunciation and an accent.  It may be a bit "uneven" in this regard, (on the Tantive IV in Star Wars he sounds particularly English and in much of the original film, whereas in Empire and ROTJ he doesn't seem nearly as British, although still having quite an English flavor to his vocal phrasing).  Furthermore, once finally unmasked in Return, Vader as Anakin Skywalker is portrayed by a longtime British (as in VERY British) stage and BBC actor, with an extremely strong and undeniably authentic, natural English accent.  

In conclusion, Anakin should have had a British accent in the Prequels. 

Luckily, I don't consider the Prequels "canon" and thus don't "have" to accept anything from those films as the true background history to the OT and the old EU (and some select current EU material) that I consider truly part of my personal SW canon.  

Additionally, I always imagined the British/English accents to be representative of the proper speech of the "Core" political worlds to the Republic and/or Empire, as in Coruscant/Had Abbadon (whatever you want to call "Imperial Center"), Alderaan, and so on), and that the "American" accent(s) generally were spoken for the following reasons: 

1.) They were from the "Outer-Rim" worlds and/or had no or too short of exposure to the "proper" Core-World pronunciation of "Basic".  Example: Luke, raised on Tatooine, and having been there his whole life away from Galactic affairs until the later in the first movie (No, that's not a typo. SW is the first movie).  "Anakin" even though, if you don't accept the Prequels as canon, he was probably born on Tatooine and lived his youth much like Luke, spent several decades in the middle of Galactic affairs prior to Star Wars and thus probably acquired the English accent after "hanging out" with Obi-Wan and all the Core-World Republic magnates and presumably living in the heart of the Republic when not embarking on "Idealistic Crusade(s)" during the Clone Wars.

2.) Alien creatures speaking the Human Language: Some, like, Yoda, have an American/Non-English accent (despite his Object-Subject-Verb word order permutation).  

3.) Characters "born" and raised in a Core world who...abandon it.  This seems to be Princess Leia (lol) who spent 18-20 years living as the Princess of the Alderaanian Royal Family.  We clearly hear her speak in a British accent (albeit a technically "false" one. Sorry, Carrie!) when she's aboard the Tantive with Vader and aboard the Death Star with Tarkin and Vader.  This hints that the English accent is the standard of diplomacy and formal conversation in the Empire, hence why Leia speaks in "one" to Vader and Tarkin in Star Wars and why almost every Imperial (if not every one) has a British accent...sans the Stormtroopers (which can be explained by them being the "commoners", perhaps?). However, whenever she's in Rebel company, she has the accent and pronunciation of a loud and proud American Girl. 

Obviously, this disparity was purposed to bring about deeply ingrained American cultural/historical positive correlations between Individualism/Freedom/Liberty/Rebellion with Americanism and the history of the American Revolution, and to effectively show the difference in "status" and rigidity/grandeur (?) between the Rebels and the "Imps", however, why this was largely lost with the Prequels and wasn't upheld with Anakin somehow, just seems...wrong. The guy got an "accent" in 20 years...and it's even stronger when his mask is off!! 

What are your thoughts?